Leadframe-based housing, leadframe strip, surface-mounted optoelectronic-component, and production method

ABSTRACT

A leadframe-based housing for a surface-mountable component, particularly a radiation-emitting component. The leadframe-based housing comprises electrical connector strips and at least one chip mounting area. One of the connector strips includes an injection aperture that enables a leadframe-based housing to be produced with a very small thickness in an injection molding process. A method for producing such housings is further specified.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage of International Application No.PCT/DE2003/001906, filed Jun. 10, 2003, which claims the benefit ofGerman Patent Application Serial No. 10234704.2, filed on Jul. 30, 2002.The contents of both applications are hereby incorporated by referencein their entireties.

FIELD OF THE INVENTION

The invention concerns a leadframe-based component housing, a leadframeribbon with pre-injection-molded component housings, a surface-mountableelectronic component, particularly a component comprising aradiation-emitting or radiation-detecting chip, for example alight-emitting diode, also known as an LED, and the method for producingsaid leadframe-based component housing.

BACKGROUND OF THE INVENTION

The invention concerns electroluminescent diode components suitable inparticular for surface-mounting on a printed circuit board, in which ahousing base body produced by injection molding and comprising partiallyembedded electrical connector strips is provided with a recess,preferably implemented as a reflector, that has a radiation window aimedat the front side of the component housing. The recess, in which anelectromagnetic-radiation-emitting chip is disposed, is filled forexample with an encapsulant that is transparent to the electromagneticradiation emitted by the chip.

Such component housings are also suitable for use withradiation-detecting chips, in which case the radiation window must betransparent to electromagnetic radiation that is to be received by thechip.

The present patent application claims the priority of German PatentApplication 10243247.3, whose disclosure content is hereby incorporatedby reference.

The invention is suitable in particular for use with radiation-emittingcomponents in which the chip is installed in a so-called premoldedleadframe. This means that each leadframe is overmolded with a housingbase body before the chip is mounted.

In the production of such a component housing, the connector strips arefirst partially stamped into a leadframe ribbon. The leadframe ribbon isthen placed in a two-part injection mold which forms a cavity around theleadframe that serves to create the housing base body.

An injection compound, e.g. a white plastic, is then fed in through aninjection nozzle, for example via the portion of the injection moldadjoining the back side of the leadframe, i.e. into the portion of thecavity adjoining the back side of the leadframe, and fills the entirecavity of the injection mold.

After the injection compound has at least partially solidified, theinjection mold is opened. As the leadframe is removed from the mold, theinjection compound located in the injection nozzle is torn away from theinjection compound located in the cavity. In addition, the chip ispreferably arranged on one of the connector strips in the recessprovided for it, connected in an electrically conductive manner to theconnector strips and provided with encapsulant. After this, thecomponents interconnected by the leadframe ribbon can be separated fromone another and thereby singulated from this interconnected structure.

A radiation-emitting component of the aforesaid kind is described, forexample, in EP 0 400 176 A1. The component comprises a housing base bodywith a mounting area in which a leadframe is partially embedded.Portions of the leadframe are formed as connector strips that projectfrom the housing base body and, as they proceed further, are bent sothat their connection areas lie in one plane with the mounting area,which defines the mounting plane of the component.

The overall height of components produced in this manner can be reducedto less than about 1 mm only with high technical outlay, if at all. Theminimum height of the front portion of the housing base body is thenabout

0.5 mm, that of the back wall of the housing base body about 0.3 mm, andthe thickness of the connector strips about 0.1 mm.

The reason for this is that the layer thickness of the injectioncompound located in the cavity between the leadframe and the tear-offsite at the injection nozzle must be great enough to preventdelamination between the back side of the leadframe and the injectioncompound, insofar as possible. Such delamination would drasticallyincrease the risk of damage to the component during further processingor later on during operation. Current knowledge has it that theabove-cited layer thickness of the injection compound must be so greatthat the mechanical tensile forces occurring in the injection compoundduring tear-off from the injection nozzle can be reduced to a level suchthat the forces exerted at the boundary with the leadframe are notsufficient to tear the injection compound away from the leadframe.

However, to permit, for example, a very small overall height on printedcircuit boards and/or complete countersinking particularly into roundopenings (bores) in printed circuit boards, the height of the componentsmust be kept as small as possible, and there is a pressing need toreduce the overall height far below the above-cited critical height ofabout 1 mm. In some applications, especially in mobile communicationterminals, the radiation-emitting components should have a much smallerheight.

The possibility of reducing the overall height of components bydecreasing the height of the housing base body on the chip side isseverely limited owing to the final height of the radiation-emittingchip. The possibility of reaching the stated goal by simply reducing thethickness of the housing base body on the back side of the leadframe isalso severely limited, since, as explained above, if the layer ofinjection compound used to form the back side of the housing is toothin, it will easily be torn away with the injection nozzle that is tobe removed during the injection process used to produce the housing, inwhich case the hermeticity and thus the operation of the component canbe disrupted.

SUMMARY OF THE INVENTION

It is, therefore, an object of the instant invention to provide aleadframe-based housing for an electronic component, particularly for aradiation-emitting surface-mountable component, that has a very lowheight; an electronic component of this kind; a leadframe ribbon; and amethod for producing a corresponding leadframe-based housing.

This object is achieved by means of a leadframe-based housing, leadframeribbon, an electronic component having the features as set forth belowand a method having the features. from following description.Advantageous improvements of the invention also follow.

A leadframe-based housing according to the invention for asurface-mountable electronic component has the following constituents:

-   -   a leadframe having a front side and a back side and comprising        at least two electrical connector strips,    -   a housing base body produced in an injection process, preferably        injection-molded or transfer-molded, and made from an        electrically insulating injection compound,    -   a front portion disposed on the front side of the leadframe and        a back wall of the housing base body disposed on the back side        of the leadframe,    -   at least one injection aperture in the leadframe, for apposing        or inserting an injection nozzle through which the injection        compound is injected onto the leadframe from a back side of the        leadframe.

The injection compound thus is injected from the back side of theleadframe through the injection aperture into the portion of theinjection mold cavity that creates the front portion of the housing basebody on the front side of the leadframe. During injection, the injectionnozzle is guided through the portion of the cavity that creates the backwall portion of the housing base body on the back side of the leadframeto the injection aperture of the leadframe. In this fashion, acomparatively large volume of injection compound with a comparativelylarge cross section is made to be adjacent the injection nozzle and thusthe tear-off region of the injection compound at the cavity end of theinjection nozzle. The risk of delamination is reduced with this type ofhousing.

The injection aperture is preferably disposed in one of the electricalconnector strips. The back wall, i.e. the plastic wall between the backside of the leadframe and the back side of the housing base body,advantageously has a thickness of 0.3 mm or less, preferably 0.25 mm orless, especially preferably 0.2 mm or less, it being understood that thethickness in each case is greater than 0 mm.

Especially preferably, the invention is suitable for use with componentsin which at least one recess for receiving a chip, particularly aradiation-emitting or radiation-detecting semiconductor chip, e.g., alight-emitting diode, is provided in the front portion of the housingbase body.

The injection aperture in this case is especially preferably arranged inthe region of a wall that is part of the front portion and delimits therecess. A large volume of injection compound is advantageously presentthere by virtue of the structural shape itself.

Provided in the recess is a chip mounting area that is preferablylocated on one of the two connector strips, but can also be arranged onthe housing base body. Such a chip mounting area can also, however, beprepared later on, for example in the form of a carrier plate that issubsequently to be placed in the recess. It is further conceivable toplace in the housing base body a thermal connecting base that preferablyextends from the floor of the recess through the housing base body tothe back side thereof.

Depending on the arrangement of its connection areas, the chip can, forexample

-   -   be electrically connected to the electrical connector strips by        means of two bonding wires,    -   be attached to one contact surface on one of the two connector        strips by an electrical connecting means and be connected to the        second connector strip by a bonding wire, or    -   be mounted in a flip-chip configuration with its connection        areas right on the strips.        Still other electrical connection variants are, of course,        feasible and will be chosen by the skilled person based on the        design of the chip concerned.

In the case of radiation-emitting components, which constitute anespecially preferable application for the present invention, the recesscomprises a radiation exit window. In this case, the inner surfaces ofthe recess are preferably implemented as a radiation reflector.

Alternatively, the entire housing can also be made of a radioparentmaterial and can completely encase the radiation-emitting chip.

The injection compound preferably comprises a synthetic material,particularly a temperature-resistant synthetic material filled withwhite filler. The synthetic material is preferably a thermoplasticmaterial and the filler is preferably titanium oxide and/or bariumsulfate.

Suitable materials for encasing the chip in the recess, for examplereaction resins such as epoxy resins, acrylic resins, silicone resinsand polyurethane resins, are known to those skilled in the art andtherefore will not be recited in more detail herein.

The same is true of the injection compound for the housing base body.Likewise, known and commonly used methods for mounting and electricallycontacting chips can advantageously be used in this case.

The method of the invention comprises in particular the following steps:

-   -   prestructuring the connector strips and the injection aperture        in a leadframe ribbon, for example by stamping, etching or laser        cutting, resulting in the formation in the leadframe ribbon of        plural adjacently (periodically) arranged component regions each        of which will subsequently be provided with a housing base body,    -   applying to the leadframe an injection mold that can have two or        more parts,    -   injecting the injection compound into the injection mold through        the injection aperture, the injection nozzle of the injection        apparatus being placed against or inserted in the injection        aperture,    -   at least partial solidification of the injection compound, and    -   opening the injection mold and removing the injection nozzle.

In the case of a housing base body comprising a recess for the chip, theinventive injection aperture is particularly preferably located under asolid wall of the housing base body that at least partially surroundsthe recess.

The particular advantage of the inventive production method resides inthe fact that the overall height of a component housing to be producedthereby can be substantially reduced by means of the particularly thinlyconstructed back wall of the component housing, especially compared tothe heretofore-known radiation-emitting components fabricated by meansof premolded leadframes.

The term “leadframe” herein relates in particular to metal leadframes ofthe kind commonly used in semiconductor optoelectronics, for example forelectroluminescent diode housings. However, the term “leadframe” as usedherein also encompasses all other leadframes suitable for the inventivehousing technology, which need not necessarily be completely of metaland for example can include a combination of electrically insulatingmaterial and electrical conductor paths formed thereon. The term“leadframe” in this case is not necessarily to be construed as acontinuous ribbon suitable for a “reel to reel” technique. Rather, theleadframe can also, for example, be in the form of strips or arrays.

Further features, advantages and improvements of the invention willemerge from the embodiment examples described hereinbelow in conjunctionwith FIGS. 1 to 4.

Therein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a radiation-emitting componentof prior art fabricated by the premold technique.

FIG. 2 a is a schematic plan view of a leadframe ribbon according to theinvention,

FIG. 2 b is an enlarged schematic plan view of two mutually appurtenantconnector strips of the leadframe of FIG. 2 a,

FIG. 2 c is a schematic plan view of a leadframe ribbon according toFIG. 2 a with inventive housing base bodies formed by injection molding,

FIG. 3 a is a schematic diagram of the plan view of a further embodimentexample of the connector strips of an inventive component,

FIG. 3 b is a schematic diagram of the perspective bottom view of aninventive housing base body with a leadframe according to FIG. 3 a,

FIG. 3 c is a schematic diagram of the perspective view from above of ahousing base body according to FIG. 3 b,

FIGS. 4 a and 4 b are schematic diagrams of a cross section through,respectively, a housing base body of a component or prior art (4 a) anda component according to the invention (4 b) during the injection of thehousing base body,

FIGS. 5 a and 5 b are schematic diagrams of a cross section through,respectively, a housing base body of a component of prior art (5 a) anda further embodiment of a component according to the invention (5 b)during the injection of the housing base body.

Like or like-acting elements have been given the same reference numeralsin the figures.

FIG. 1 is a perspective diagram of a surface-mounted componentcomprising a housing of prior art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The housing base body of rectangular outline illustrated in FIG. 1 has afront portion 8 a and a back wall 8 b, a reflector recess comprising aradiation exit window 12 being provided in the front portion 8 a. Afirst connector strip 2 a and a second connector strip 2 b are partiallyembedded in the housing base body and are connected to aradiation-emitting chip that is not shown here (it being hidden insidethe housing base body). The projecting portions of the connector strips(external contacts) serve for contacting the component, e.g. to anexternal printed circuit board. The external contacts can extendperpendicularly to the corresponding side wall of the housing or, asindicated in broken lines in FIG. 1, they can be bent around the housingbase body.

The leadframe ribbon 1 according to the embodiment example of FIGS. 2 aand 2 b is prestructured, for example by stamping, and comprises inparticular a plurality of first connector strips 2 a and a plurality ofsecond connector strips 2 b, which are separated from the leadframeribbon along lines 3 a and 3 b, respectively, in a subsequent methodstep.

Contact strips 2 a and 2 b are intended respectively as the cathode andanode connections of the components to be produced. Additionalstructures (e.g. heat-conducting strips) can also be provided on theleadframe ribbon. In this embodiment example, a chip mounting area 14for a chip is provided on connector strip 2 a and a wire connecting area13 for a bonding wire is provided on connector strip 2 b. Providedaccording to the invention on first connector strip 2 a is an injectionaperture 24 into which an injection nozzle can be inserted during thecreation of a housing base body by injection molding. The injectionaperture can alternatively be provided in second connector strip 2 b. Itis advantageous for each injection aperture to be provided under arespective side wall, of the housing base body, that is to be formedlater on.

Chip mounting area 14 and wire connecting area 13 of the leadframeribbon respectively extend (in the finished housing base body) into aprovided reflector recess or have one surface that is contiguous atleast with the interior of the recess, and thereby form at least part ofthe floor of the recess. To further reduce the size of the housing basebody, a separate recession leading to the wire connecting region canadditionally be formed in the reflector recess. These aspects candiscerned in FIG. 3 c.

Further formed in leadframe ribbon 1 are circular openings 6 a and 6 bfor guiding and transporting the leadframe ribbon.

In addition, connector strips 2 a and 2 b preferably compriserectangularly shaped openings 21 suitable for relieving loads on thecomponent housing during the bending of the connector strips (seeFIG. 1) or anchoring the connector strips in the component housing.

FIG. 2 c shows the leadframe ribbon 1 with a housing base body 100produced according to the invention by an injection method andcomprising in each case a chip mounting area 14 and a recess leading toeach of said chip mounting areas.

The embodiment example illustrated in FIG. 3 a, representing a leadframeof an inventive housing and component of substantially circular outline,comprises sickle-shaped connector strips that serve to improve theanchoring of the connector strips in the housing base body and toprovide elastic strain relief during the bending of the connectorstrips. This leadframe as well comprises an injection aperture 24,disposed next to a chip mounting area 14, into or in apposition to whichan injection nozzle can be guided from the back side of the leadframe toproduce the housing base body.

FIG. 3 b shows an inventive housing base body 100 of substantiallycircular outline in a perspective view from below. Visible here is theinjection aperture 24, through which the housing base body 100 isinjected into the cavity of a suitable injection mold into the portionof the cavity adjoining the front side of the leadframe. In otherrespects, the front portion of housing base body 100 is configured asillustrated in FIG. 3 c, for example. This type of housing isparticularly suitable for the production of surface-mountableradiation-emitting and/or radiation-detecting components comprising LEDand/or photodiode chips that can be at least partially sunk intocircular openings in printed circuit boards or the like.

The component depicted in FIG. 3 b is shown in a perspective view inFIG. 3 c. A radiation-emitting chip 16, for example an LED chip, isfastened in a reflector opening, for example on connector strip 2 a. Ametallic solder or a conductive adhesive, for example, is used as theconnecting means. A second contact of the LED chip is electricallyconnected to connector strip 2 b, for example by means of a bonding wire17 a. The side wall 11 of a recess, which connects the floor of therecess to the outer surface of housing base body 100, is implemented sothat it acts as a reflector surface for electromagnetic radiationemitted by the chip 16. It can advantageously be shaped as planar,concave or otherwise, depending on the desired radiating behavior. Theprojections 10 a, 10 b and 10 c on the housing base body that can beseen in FIG. 3 c serve to guide the connector strips located outside thehousing base body. They can additionally serve as insertion bevels forinserting the housing into openings in a printed circuit board.

On the front side, which faces away from the connector strip, the chip16 has a contact area from which an electrical connecting line 17 (e.g.a wire connection) is led to wire connecting part 13.

The particular advantage of the invention is made immediately apparentby the comparison of the prior art and the invention illustrated inFIGS. 4 a and 4 b.

The front portion 8 a of housing base body 100, which is intended, forexample, for the subsequent mounting of an LED chip, has in both cases areflector recess in the form of a frustum-of-a-cone-like opening thatbroadens in the direction of the main radiation direction and possessesa radiation exit window 12. The reflector recess is filled with atransparent encapsulant 41.

A chip 16 to be inserted in a subsequent process step and an electricalconnecting line 17 are depicted schematically in dashed lines.

The oblique side face 11 of the recess preferably serves as a reflector.

The housing base body 100 is made by means of a two or more partinjection mold that has a cavity for housing base body 100 in which theleadframe is placed during the injection process. The cavity of theinjection mold is filled with an injection compound for the housing basebody by means of an injection nozzle 23.

The difference between the prior art and the inventive arrangement ofthe injection nozzle lies in the position of the injection nozzle 23. Inthe prior art, the injection compound is injected into the volumeadjacent the back side of the leadframe. After the injection compoundhas solidified, the injection nozzle is detached from the injectionmold. This produces a tear-off site 25. During the detachment of theinjection nozzle, the region near the tear-off site is subjected tosevere mechanical loading that can lead to delamination of the materialof the (solidified) injection compound at the interface between the backwall 8 b of the housing base body and connector strips 2 a and 2 b.Thus, back wall 8 b can easily become damaged if its height is verysmall. To prevent this insofar as possible, the back wall 8 b of thehousing base body must have a relatively large thickness.

In a leadframe-based housing according to the invention, by contrast,the injection nozzle 23 is not inserted in the central region of acavity suitable for producing the back wall 8 b of the housing basebody, but is placed against an injection aperture 24 disposed laterallyin the leadframe, or is inserted into said injection aperture 24. Thetear-off site 25 thus is not located opposite the leadframe, but isinstead adjacent the volume of injection compound constituting the solidside wall of the housing base body. This makes it possible to producethe back wall 8 b of housing base body 100 with a minimal thickness, andthus a component having a minimal overall height. A back wall thicknessof less than 0.3 mm, for example 0.1 mm, can be attained.

Due to the very small height of the back side of an inventive component,formed by the back wall of the housing base body, the space occupied bythe component in the vertical direction is much smaller than that of acomponent of prior art. The inventive component is suited in particularfor flat display modules or as background illumination, for example fora liquid crystal display.

FIGS. 5 a and 5 b each illustrate an injection mold 200 comprising acavity 210. In the fabrication of a housing base body, it is importantthat electrical connection areas 20 a and 20 b of connector strips 2 aand 2 b, which are intended to place a chip in electrically conductivecontact with connector strips 2 a and 2 b, not be covered with injectioncompound.

In the injection mold 200 of prior art illustrated in FIG. 5 a, theinjection compound is injected from below through injection nozzle 23toward connector strips 2 a, 2 b, causing connector strips 2 a, 2 bcomprising electrical connection areas 20 a and 20 b to be pressedagainst the injection mold (the path of the injection compound duringinjection is indicated by arrows). This seals off connection areas 20 a,20 b insofar as possible, thus reducing the risk of connection areas 20a, 20 b being covered with injection compound.

By contrast, in an injection mold 200 for a component housing accordingto the invention, as illustrated in FIG. 5 b, the injection compound isinjected into the cavity 210 via the injection aperture 24 in suchfashion that no pressing of the connection areas 20 a and 20 b againstthe injection mold as described in the preceding paragraph occurs. Thereis instead a risk that the connector strips 2 a, 2 b and thus theconnection areas 20 a, 20 b will be pushed away from the injection moldand a gap will form between the upper inside wall of the injection moldand connection areas 20 a, 20 b, which will then cause connection areas20 a, 20 b to be covered (the path of the injection compound duringinjection is again indicated by arrows).

To keep connection areas 20 a, 20 b from being pushed away from theupper inside wall of the injection mold 200 during the procedureaccording to the invention, an injection mold 200 for a componenthousing according to the invention (cf. FIG. 5 b) is shaped so that inthe closed state, with connector strips 2 a, 2 b clamped inside, it alsoabuts, with an inner face, the surfaces of connector strips 2 a, 2 bopposite connection areas 20 a, 20 b. Connector strips 2 a, 2 b arethereby pressed, in a region of connection areas 20 a, 20 b, againstsections 201 a and 201 b of the appurtenant inner wall of the injectionmold in such fashion that they are sealed off. Such an injection mold200 for producing an inventive component housing therefore greatlyreduces the risk that connection areas 20 a, 20 b will become coveredwith injection compound during the transfer molding of a housing basebody.

A housing base body produced with an injection mold 200 of this kindcomprises recessions in the back wall of the housing base body inregions of connector strips 2 a, 2 b located opposite connection areas20 a, 20 b. The surfaces of connector strips 2 a, 2 b that are outwardlybare in these regions can be electrically insulated outwardly later on.This can be done, for example, by coating them with an electricallyinsulating material, for example electrically insulating varnish.

The description of the invention with reference to the illustratedembodiment examples is naturally not to be construed as a limitation ofthe invention. For example, the chip can be mounted—adhesive-bonded, forexample—directly on a chip mounting area of housing base body 100, andthe chip can be electrically connected to the connector strips by meansof wire connections alone. The chip can also be mounted on a separatethermal connector embedded in the housing of the component and again beconnected electrically to the leadframe via wire connections. Othervariants of the chip mounting technique that are not described here canalso be used. None of these embodiments departs from the basic ideas ofthe instant invention. The invention is not limited to the number orparticular implementations of the embodiment examples illustrated in thefigures. Rather, the invention encompasses any novel feature and anycombination of features that includes in particular any combination offeatures recited in the claims, even if this combination is not statedexplicitly in the claims.

1. A surface-mountable leadframe-based housing for an electronic component, with a leadframe having a front side and a back side and comprising at least two electrical connector strips, and an injection-molded or transfer-molded housing base body made from an electrically insulating injection compound and comprising a front portion disposed at the front side of said leadframe and a back wall disposed at the back side of said leadframe, wherein said leadframe comprises at least one injection aperture through which said housing base body is injected onto said leadframe from a back side of said leadframe, and wherein the back wall of the housing base body includes a first recess that extends from said injection aperture.
 2. The housing as described in claim 1, wherein said injection aperture is disposed in one of said electrical connector strips.
 3. The housing as described in claim 1, wherein said back wall has a thickness of less than 0.3 mm and more than 0 mm.
 4. The housing as described in claim 1 for a radiation-emitting and/or radiation-detecting component, wherein said housing base body comprises in said front portion a second recess for receiving a radiation-emitting and/or radiation-detecting chip, said injection aperture being disposed in the region of a wall of said front portion delimiting said second recess.
 5. The housing as described in claim 4, wherein said second recess is formed as a reflector.
 6. The housing as described in claim 4, wherein said second recess is filled with an injection compound that is transparent to radiation emitted by and/or to be detected by said chip.
 7. The electronic component comprising a housing with reference to claim 4, wherein said second recess is filled with an injection compound that is transparent to radiation emitted by and/or to be detected by said chip.
 8. A leadframe ribbon comprising at least one housing as described in claim
 1. 9. An electronic component having a housing as described in claim 1, which comprises at least one chip.
 10. The electronic component as described in claim 9, wherein said at least one chip is a radiation-emitting and/or radiation-detecting chip.
 11. The electronic component as described in claim 9, wherein said chip is disposed on one of the two connector strips and is electrically connected to the second connector strip by means of an electrical connecting line.
 12. The electronic component as described in claim 9, wherein said chip is disposed on a mounting area of said housing base body and is electrically connected to each of said electrical connector strips by means of in each case one electrical connecting line.
 13. The electronic component as described in claim 9, wherein said chip is disposed on a thermally well-conducting chip carrier leading through said housing base body to the back side and is electrically connected to each of said electrical connector strips by means of in each case one electrical connecting line.
 14. A method for producing a lead frame-based housing, comprising: a) providing a lead frame having a front side and a back side, the lead frame comprising two connector strips, at least one of the connector strips having an injection aperture, b) applying to said lead frame an injection mold that forms around said lead frame a cavity for creating a housing base body having a back wall that includes a first recess that extends from said injection aperture and placing an injection nozzle proximate to said injection aperture, c) injecting an injection compound into said cavity from the back side of the lead frame, d) causing the injection compound to at least partially solidify, and e) removing the injection nozzle and opening the injection mold.
 15. The method as described in claim 14, wherein a thermoplastic material is used as the injection compound. 